G protein-coupled receptors (GPCR) are seven-transmembrane receptors and are responsible for actions to transduce the signals of hormones, neurotransmitters, cytokines and other molecules, across the cell membrane.
Human GPR52 (Molecular Brain Research, 64, 193-198, 1999) is one of GPCR, for which no ligand has been reported, and its role or function has also not been reported.
It is known that reserpine (formula below) is an alkaloid contained in Rauwolfia serpentina and has a central depressant effect and hypotensive effect (Am. J. Chin. Med. 7, 197-236, 1979). Reserpine is used as a drug for improving schizophrenia, antipsychotic drug, hypotensive drug and sedative.

Methoctramine (formula below) is known as an antagonist of muscarinic acetylcholine receptor M2 (Eur. J. Pharmacol., 144, 117-124, 1987).
